Multi-Carrier Distributed WDM Ring Network Based on Reconfigurable Optical Drop-Add-Drop Multiplexers and Carrier Wavelength Reuse

This paper presents and experimentally demonstrates a multi-carrier distributed wavelength-division-multiplexing (WDM) ring network based on reconfigurable optical "drop-add-drop" multiplexers for regional and metro network applications. In the "drop-add-drop" network, optical carriers generated by a centralized multi-carrier light source (MCLS) are "dropped" at the source nodes and used for uplink transmission. Data are "added" to the network by external modulation of one or more carriers. Data are then "dropped" at the destination nodes. The reconfigurable optical add/drop multiplexer (ROADM) at each access node is not only used to "add" and "drop" data, but also to "drop" carriers, which eliminates the many distributed laser-diodes used in the conventional network. In this work, we successfully demonstrate, for the first time, a "drop-add-drop" network experiment offering 10 Gbit/s WDM transmission. Moreover, to dramatically improve the utilization efficiency of the carrier wavelengths distributed by the MCLS in the "drop-add-drop" network, we introduce the carrier wavelength reuse technique which sets the carrier extraction circuits in each access node. This technique enables us to reuse the carrier wavelengths that were already utilized for data transmission between prior source and destination nodes. To evaluate the effect of carrier wavelength reuse, we compare the blocking probabilities of the "drop-add-drop" networks with and without carrier wavelength reuse. The results show that wavelength reuse dramatically reduced the blocking probability. In addition, we numerically analyze the advantages of the "drop-add-drop" network over the conventional ROADM network in terms of network cost and power consumption.